The invention relates to a method for reducing valve opening and closing time durations for a valve that is mounted upstream from a charge changing (intake) valve in an intake duct of a reciprocating engine. The invention also relates to a valve to be mounted in an intake duct of a reciprocating engine upstream from a charge changing valve.
Mounting in the intake port of a reciprocating engine, upstream from an intake valve, of an additional valve which remains closed during the intake stroke of the piston with the intake valve open, so that a high negative pressure is built up downstream from the additional valve, is known in the prior art. If the additional valve is then opened, high impetus is imparted to the fresh charge admitted because of the negative pressure, as a result of which the filling of the combustion chamber is increased and greater torque is achieved. It is advantageous for numerous applications if the switching times, that is, the period of time within which the opening cross-section of a fluid channel controlled by a valve element of the additional valve is fully opened or closed, is as short as possible.
Reducing the switching times of valves entails considerable expense if the valve element is not permanently in motion, for example, in rotary motion in the case of a rotary slide valve. Even if the valve element is part of a mechanical oscillator kept in its end positions by electromagnets, limits are imposed on the switching times, since neither can the weight of the oscillator, because of considerations of strength, density, and cost, be lowered optionally as greatly as possible, nor can the spring rigidity, because of considerations of weight and cost, be optionally increased as greatly as possible nor can the retaining power of the electromagnet, because of considerations of space and energy requirements, be increased excessively.
DE 195 90 501, the independent claims presented in the preambles of which are taken as the basis, discloses a valve with a valve flap (valve element) mounted in the intake port of a reciprocating engine upstream from a charge changing valve which is hinge-connected by linkage to a bar rigidly connected to an armature, which armature is pretensioned in a central position between two electromagnets by two springs. When in contact with an electromagnet the valve flap is in its full open position, in which it is oriented toward the longitudinal center of the intake port. When the armature is in contact with the electromagnet the valve flap is in its closed position, in which it closes off the cross-section of the intake port. During the end portion of movement of the valve flap into its closed position or from its closed position, the edge of the valve flap moves along a suitably shaped recess in the interior wall of the intake port, so that the valve opening cross-section cleared by the valve flap changes only if the valve flap has passed over the edge of the recess or a control edge formed there. The result achieved is that the change in the valve opening cross-section at the beginning of opening of the valve and at the end of closing of the valve takes place very rapidly, so that precise control times may be established for commencement of opening and completion of opening.